Apparatus for the diffusion of substances between two fluids via semipermeable membranes are well known, and various constructions are shown in U.S. Pat. No. 3,411,630; U.S. Pat. No. 3,501,011; U.S. Pat. No. 3,511,381; U.S. Pat. No. 3,516,548; and U.S. Pat. No. 3,734,298. In such patents, the membranes are arranged in pairs between each pair of adjacent spacer plates, with one fluid, such as blood, being conducted between the membranes, while another fluid, such as purifying liquid or oxygen, is conducted outside the membranes between the membranes and the adjacent spacer plates. However, there also exists in the prior art, dialysis devices which include alternately-arranged single membranes disposed between single spacer plates.
Such prior art constructions have had problems with respect to achieving a satisfactory emptying of the fluid from the devices following their use. This problem is particularly significant when the device is used for the purification of blood, and the maximum amount of blood possible must be returned to the patient when the device is emptied.
Broadly, it is an object of the present invention to provide an improved device which overcomes the aforesaid problem. Specifically, it is within the contemplation of the present invention to provide an improved device which is constructed to provide a more complete emptying of the fluid from the device after its use and includes horizontal flow passages laid out in the shape of a V, and wherein vertical flow passages are preferably located as close as possible to the point of the V.